Numerous types of float shoes and float collars have been devised. A float shoe is a type of downhole valve that is used at the lower end of a tubular string and is conventionally adapted to be a float collar and to support another tool or a length of tubular below the collar. The float shoe is functionally similar to a float collar, but conventionally has a rounded lower end with no equipment beneath the shoe. Many float shoes include one or more poppet valves that are controlled by fluid pressure to open and close off a flow of fluid through the tool.
The following U.S. patents relate generally to float shoes and collars: U.S. Pat. Nos. 6,173,457, 6,199,221, 6,311,775, 6,334,487, 6,390,200, 6,401,824, 6,467,546, 6,491,103, 6,497,291, 6,513,598, 6,679,336, 6,684,957, 6,712,145, 6,772,841, 6,802,374, 6,962,163, 7,029,274, 7,101,176, 7,234,522. Swellable packers are disclosed in U.S. Pat. Nos. 2,814,947, 2,945,541, 4,137,970, 4,520,227 and 4,633,950, and Publications 2005/0199401 and WO 02/20941.
The disadvantages of the prior art are overcome by the present invention and an improved float shoe and float collar are hereinafter disclosed which use a swellable elastomer to reliably close off the flow port through the tool.